沪通公铁两用长江大桥新型全焊箱-桁组合节点受力性能研究
Research on mechanical behavior of new type box girder-truss composite welded integral joints of Hutong Yangtze river rail-cum-road bridge

在建的沪通长江大桥是目前世界上跨度最大的公铁两用斜拉桥,通行4线铁路、6车道公路,孔跨布置为:(142+462+1 092+462+142)=2 300 m。下层铁路桥面系为2.2 m高的封闭式正交异性板钢箱梁,主桁节点欲采用新型全焊箱-桁组合节点,节点板将主桁相关杆件和铁路桥面系钢箱梁连成一个整体,节点外形简洁,但内部结构构造和受力状态都很复杂,各构件内部加劲肋众多,形式、尺寸多样。在全桥空间有限元分析的基础上,选取具有代表性的E60中桁节点和两个最不利的主力组合工况,完成了局部精细有限元分析和1:3的缩尺模型试验。结果表明,E60中桁节点各相关构件绝大部分区域的应力水平不高,Mises等效应力小于200 MPa,实测结果与有限元分析结果吻合较好。但在节点板与斜杆连接处的边缘、节点板与下弦杆顶板、横隔板等多板连接处的边角处有应力集中现象,有限元分析的局部最大Mises等效应力超过200 MPa,但都小于材料Q370qE的屈服应力。试验所得的离有限元计算最高应力点2~4 cm处的实测应力都远小于有限元计算的最大应力值,表明边角处的高应力范围很小,很局部。这种新型全焊箱-桁组合节点结构构造合理,受力性能良好,安全,可以在沪通公铁两用长江大桥上应用。
Hutong Yangtze river bridge under construction is a rail-cum-road cable-stayed bridge with the largest span in the world. Four line railways and six lanes are arranged on the bridge and the span of the bridge is 142+462+1092+462+142 = 2300m. 2.2m height closed steel orthotropic plate box girder is used as the railway floor system. A new type box girder-truss composite welded integral joint are tended to be adopted as the lower main truss joint. Using two connecting plates the relevant truss bars and steel orthotropic plate box girder of the railway floor system are welded as a whole. The appearance of the joint looks concise but the internal structure construction are very complex. Many stiffening ribs of various kinds and scale are arranged inside every components. Refined finite element analysis and 1:3 reduced scale model test were completed for the representative E60 middle truss joint and the two worst load cases of main loads combination based on 3D finite element analysis of the whole bridge. The results show that the stress level of most areas of the relevant components of E60 middle truss joint are not high, and their Mises equivalent stress is less than 200 MPa. The test results are well coincided with that of the finite element analysis. But stress concentration exists at the joint plates edges connecting with the inclined web member and at the multi-plate connecting corners such as the joint plate connecting with the top plate of the lower chord and the diaphragm plates, where the maximum Mises equivalent stress is over 200MPa but less than the yield stress of Q370qE according to the refined finite element analysis. The tested stresses of the testing points which are away the finite element maximum stress point 2 to 4cm are far less than that of the finite element analysis, which shows that the high stress areas are very small and local, and the structure of the new type welded integral joints is reasonable, its behavior is good and safe, which indicates that this new type of box girder-truss composite welded